How to get better VRay renders (aka working in linear space)

[jujubee]

That sounds like the same thing which I'm experiencing - washed out colors For the most part, lighting seems very accurate but there is a noticeable lack of contrast and the colors are subdued. Photoshop could fix it but it would be nice to get a more accurate representation out of Max. Any ideas anyone?

[flipside]

Ok.... Starting to see thru the haze a bit, but still confused on the end of the process.

I have MAX gamma set to 2.2. I have been using 'gamma correction' in the color mapping with 1.0 and 0.4545.

When I render to VFB, the image looks pretty good. (ie - not far off from what I would deliver to a client) When I click the 'Duplicate to MAX buffer' button, the image shown is WAY lighter and washed out. If I save from either the VFB or the MAX window, I get the same result. If I override output gamma at save time, gamma=1.0 gives a good looking image (just like VFB), and gamma=2.2 gives me a washed out image (just like MAX window). Additionally, if I click the 'Show in sRGB space' button in the VFB, the image gets considerably darker.

So for starters, I need to know two things (given the above workflow, color mapping, etc.):

#1 - Which saved image is "linear"?

#2 - If I assign an override material to render a neutral grey image to evaluate lighting, do I evaluate it in the VFB or in the MAX window?

Well this is quite normal. When you use gamma color mapping, the gamma is burned into the image. So the image is created in linear space, and converted to gamma 2.2 by the color mapping. This looks good in vray vfb and also when you save it.

But! the vray vfb is not affected by the display gamma! The max vfb is though, so if you copy your already gamma corrected image to the max vfb, it gets corrected twice there, hence the very light image.

You have several choices. If you use the vray vfb, remember it is not affected by the display gamma of max. So if you want to see the correct output in it, you need to gamma correct it. You can do this by doing 1 of these 3 things:
1. use gamma color mapping. Note that the gamma is burned into the image already.
2. Apply throbs curve in the vray vfb
3. press the srgb button in new vray versions
In these last two, the image remains gamma=1.0, only it's display is changed to 2.2 by the curve or the button. Haven't tried these yet but I guess if you just press save, the curve correction or srgb correction are not saved along.

See also this thread for some more side effects of using gamma color mapping or not:
http://www.chaosgroup.com/forum/phpB...r=asc&start=25

So if you don't use the vray vfb, or you copy your image from vray vfb to max vfb, you must take care not to gamma correct it twice. If you use max vfb AND gamma color mapping correction, you must set display gamma to 1.0 to show it properly. This is no good because then you can't see material previews and viewports good, they will be too dark.

Your confusion is simply because vray VFB isn't affected by max's display gamma...

Also note that display gamma isn't saved with the image. So if you use max vfb and display gamma=2.2, your image will look good, and if you save it and view it outside of max, it will look way too dark. That's why you get 2 identical images if you copied the vray vfb to max's and saved them both (altough they look very different inside max).

Hope this makes sense. There is definately a need for a step by step tutorial about all this, on a simple scene... I think the gnomon dvd's have this, not sure. I was thinking about making one with my appartment scene that was used by vlado to make the interior lighting tutorial, guess it would be a nice addition.

[CCS]

Ok, now I'm really confused.

You have several choices. If you use the vray vfb, remember it is not affected by the display gamma of max. So if you want to see the correct output in it, you need to gamma correct it. You can do this by doing 1 of these 3 things:
1. use gamma color mapping. Note that the gamma is burned into the image already.
2. Apply throbs curve in the vray vfb
3. press the srgb button in new vray versions
In these last two, the image remains gamma=1.0, only it's display is changed to 2.2 by the curve or the button. Haven't tried these yet but I guess if you just press save, the curve correction or srgb correction are not saved along.

I'm already doing #1 (gamma correct color mapping). So does this mean I'm creating an image that is *not* linear? If so, why in the world would I want to do that? I thought the whole point of this exercise was to stay in linear space up until the end!

I don't like the curve option because I have to set it every blasted time. Can't just set it as the default. Same goes for #3.

I like some of the features of the VFB, but it's seeming like more of a problem in some ways.

I'd really like to try working in this "linear space", but so far I haven't seen a "linear space workflow". I've seen things called that, but they have been very good introductions to what linear space is - not a workflow, or step by step beginning to end how this would work on a typical project.

====

For instance, my typical workflow is to rough model and light a project, assign an override material, and do some test renders to evaluate lights, GI, etc.
** How can I do this in linear, without having to jump thru hoops?

Then once I have something I can use, I'll start applying materials. Then I'll render some previews to send to client to pick camera positions.
** How do I save images out that are "correct"?

Then once I've run thru all the iterations of lighting, materials, view, model refinement, etc. I'll render final images - either stills or animation frames.
** How do I do this from the "linear workspace" to end up with something that is suitable for web, print, or video (as required) ???

====

I've spent quite a bit of time trying to get my head around this, but I'm still not understanding the process or the results. I need to either get this to make sense to me, or go back to what I know works to get the jobs out. I'd like to try this workflow, but it's still not clicking.

[jujubee]

So if you use max vfb and display gamma=2.2, your image will look good, and if you save it and view it outside of max, it will look way too dark.

I completely agree with your points except this seems misleading. If you save it out of Max 8 as a HDR or EXR (from Max FB or save dialog iwth Max preferences gamma set to 2.2) it looks the same in PS CS2. If you viewed it in VFB (without applying throbs curve) and save out as HDR/EXR, it will look brighter and more accurate in PS.

As for CCS's problem as well as mine, if you're using gamma correction rollout 1 dark and .45454 bright, the end results still seems a little washed out IMO. The washed-out colors can be adjusted post-process witth Exposure lowering an EXR in PS. I'm not sure if this is a common issue or if there's any other way around it besides playing with the Dark Gamma Correction value in the rollout.

[jujubee]

1. use gamma color mapping. Note that the gamma is burned into the image already.

The gamma isn't burned into the VFB preview. However, it will appear in the Max FB if you had set your preferences to 2.2.

I've spent quite a bit of time trying to get my head around this, but I'm still not understanding the process or the results. I need to either get this to make sense to me, or go back to what I know works to get the jobs out. I'd like to try this workflow, but it's still not clicking.

Well, I've got a deadline to make on my end. But the amount of time I've spent on figuring this method out (even if it's not completely correct, ie. slightly washed-out colors - I can readjust in PS) was well worth it as my results are possibly the best method of rendering a scene without having to have resorted to complete trickery. I think it will save days off of a large project (and hundreds of hours a year) cause now I can avoid constant rerendering and testing of different color mapping methods.

[flipside]

1. use gamma color mapping. Note that the gamma is burned into the image already.

The gamma isn't burned into the VFB preview. However, it will appear in the Max FB if you had set your preferences to 2.2.

The gamma is burned in, that is what color mapping does, it applies the gamma already during ir map calculations etc, just look at the examples in the other thread I posted.

You confuse me about your questions, I'm not really sure what you mean, so I won't try to answer them.

It is really simple, you just need to make sure you don't apply gamma correction twice, and you should note that display gamma only corrects the display of the render, not the actual rendering. (and the display gamma does NOT affect the vray VFB, only the max one!!!)

I understand what you say about not being in linear space anymore, and I also wondered about that because in the beginning they say you should stay in there untill the end. This is so because post work in PS is better done in linear space (see the aimdtp site). Since I don't really care about this, because I never had problems with post work being screwed up in PS, I simply use the gamma color mapping and don't care about the fact that it isn't linear anymore. But note that you can still do linear post processing to this image in ps, you just need to use the correct color profiles and make sure you do this to highest bit depth images possible. But I'm not familiar with color profiles so this is only how I see things, not sure if it is theoretically correct.

The advantage imo is like jujubee says, not the post work in linear space being better, but the fact that lighting is way more real. You don't need to use tricks like fill lights anymore, and rendertimes will be faster for the same lightness of an image for various reasons (you don't use that high light multipliers anymore etc...). You may think, why not just render as I used to do, and apply a gamma 2.2 in PS afterwards. This will result in poor quality, doing it in floating point while rendering is much better. (again this is how I think it is...)

So if I were you, don't care about the render being linear or not, just use the gamma color mapping always, together with vray vfb. To avoid applying a second time gamma 2.2 to your saved image, leave the global bitmap saving gamma to 1.0.

And juju, what you say about slight differences between look of the VFB and photoshop, this sounds more like wrongly calibrated things and different color space in PS than in your windows system.

And slightly washed out look can also be due to not well calibrated monitor!!! But even in the old workflow, I always got nicer renders after some post work than straight out of max. So I guess it is no different with this workflow.


As a final note, I only try to help with the limited knowledge and understanding that I have about this matter. So better wait for the real experts to come in and cleaning up the mess I made here. I just wanted to help you guys while Gijs and the others are not on the board

[flipside]

So if you use max vfb and display gamma=2.2, your image will look good, and if you save it and view it outside of max, it will look way too dark.

I completely agree with your points except this seems misleading. If you save it out of Max 8 as a HDR or EXR (from Max FB or save dialog iwth Max preferences gamma set to 2.2)

Ah now I see, what I said is only true if you leave the bitmap output gamma set to 1.0. When you would use gamma color mapping AND bitmap output gamma=2.2, you're applying gamma correction twice again. Or if you don't use gamma color mapping and use the bitmap output gamma=2.2, you're burning in the gamma once. That is exactly the reason why I don't use these global settings, they're way to confusing about what you're actually doing.

[cecil gittens]

oK guys, what i have been doing eversince looking at chris's DVD is to set gamma to 2.2 in the preferences and use gamma correction for my color mapping. 1 for the dark M and 0.434 for the Bright M. This seems to be working i dont need as much light to light my seans, most of the times the sunlight and the skylight will do. Dont need the vray light in my windows. What i dont know yet is gamma 2.2 is the same for my labtop (all of my renderings is done on my labtop). Still confuse but using these settings works, for now i will accept it and try not to understand it.

Cecil G

[flipside]

oK guys, what i have been doing eversince looking at chris's DVD is to set gamma to 2.2 in the preferences and use gamma correction for my color mapping. 1 for the dark M and 0.434 for the Bright M. This seems to be working i dont need as much light to light my seans, most of the times the sunlight and the skylight will do. Dont need the vray light in my windows. What i dont know yet is gamma 2.2 is the same for my labtop (all of my renderings is done on my labtop). Still confuse but using these settings works, for now i will accept it and try not to understand it.

Cecil G

And are you using vray VFB then I suppose?

[cecil gittens]

yes, I stop using the max buffer, but my main question is. is 2.2 gamma the same for a rerular monitor as for a flat screen such as my labtop?

Cecil

[jujubee]

I got involved cause one of my interiors was so dark and someone said that I should reread these threads. It's corrected the issue completely (99% satisfaction) with the only problem now being very slight, washed-out colors.

And juju, what you say about slight differences between look of the VFB and photoshop, this sounds more like wrongly calibrated things and different color space in PS than in your windows system.

Perhaps. I've always calibrated my monitors - especially since I run dual monitors and the colors between the two by default are way far off. The AIM-DTP site helped tremedously with their charts and especially by setting up Dark/Bright points over Adobe Gamma's method (were you kill external light sources and match the monitors vertical edges.) They match pretty exact now.

As for working in PS, I've pretty much left the working colorspace as is (Adobe RGB) and haven't touched it. I tried using the new monitor's profile in PS and it didnt make much of a difference - still some slightly washed out results.

As a final note, I only try to help with the limited knowledge and understanding that I have about this matter. So better wait for the real experts to come in and cleaning up the mess I made here. I just wanted to help you guys while Gijs and the others are not on the board

LOL. Same exact sentiments. Hope I didn't mess anyone up either but I guess it's good us 'beta testers' are around. I just wonder how the heck Throb and GIJs figured this methodology out on their own...

[CCS]

Thanks for the continued help guys. I'm trying. I have a feeling I'm making it more complicated than it needs to be, but having 6 places to adjust these settings in each app isn't helping!

BTW, I ended up using my nVidia driver to adjust monitor gamma. Same settings (although a little more control in each slider), but the best part is I was able to set gamma for each monitor independently for the first time. Now they match fairly closely even though they are very different monitors.

Anyway, here are a couple renders. Pretty generic render settings. Lit only by a direct light (int=1.0) and GI (also at 1.0). What do you think? Shadows feel a little light to me, and it's significantly less saturated than my previous image. Not sure which I prefer, or which is "right".


Override mat:



With all mats on:



Again, just to make sure my head is in the right place, system gamma is 2.2, using gamma color map (1.0 / 0.4545), rendered to VFB, then saved from VFB with gamma=1.0. (Sized in PS, but no other adjustments made.)

[jujubee]

The lightness (washed out grey) looks about on target with mine. Here are my results broken down. All have the same settings other than what is specified. Nothing has been postprocessed:

Throb's method. 1/1 Liner ColorMapping:


GIJs method. 1/.45454 Gamma Correct ColorMapping:


.45454/.45454 Gamma Correct ColorMapping (in order to get the shadows darker/more contrast):


As you can see, the colors are somewhat bland - but this could easily be adjusted in PS. I was just hoping to achieve most of this straight out of the render...

[CCS]

I hear ya. I'm not against PS post. I've done it for this long, why stop?

I agree though. I'd like to get truer color, more contrast, etc. out of MAX/vray without any additional steps.

There is always the contrast/saturation in the GI rollout... But vray help says it's post-processing, and that the default settings are accurate to real-world conditions. (or something like that)

Still watching the thread.

Re: your images
I don't necessarily think that they are desaturated too much. I think that is your lighting, or maybe a couple specific materials. I also think a contrast bump would help with the perceived saturation.

What do you think of my exterior above? Does it look low contrast to you? How about sat.?

[jujubee]

I'm trying one more thing as I write. I went back to the AIM-DTP site and checked my monitors actual gamma space and it's on target for 2.5. So I've set Max gamma to 2.5 and the bitmaps input to 2.5. I've left diffuse mats with the colorcorrect at 2.2 cause im too lazy to go back and change all the settings right now. But the bitmaps and overall value should speak volumes if I'm heading in the right direction. Also, I've changed Vray GC to 1/.4 - .4 being the result of 1/2.5. Perhaps this will introduce more color and contrast.

I don't necessarily think that they are desaturated too much. I think that is your lighting, or maybe a couple specific materials. I also think a contrast bump would help with the perceived saturation.

Nah - I've been up and down that road for two days now. The bitmaps are correct. I think the rendering results is FUBAR.

What do you think of my exterior above? Does it look low contrast to you? How about sat.?

It's very hard to tell from the lack of objects, shadows, or an appropriate image reference.